Low-sulfur consumable lubricating oil composition and a method of operating an internal combustion engine using the same

ABSTRACT

This invention relates to a low-sulfur consumable lubricating oil composition, comprising: a base oil; an acylated nitrogen-containing compound having a substituent of at least about 10 aliphatic carbon atoms; and a sulfur content of about 5 to about 250 ppm; said composition being characterized by the absence of an extreme-pressure additive comprised of metal and phosphorus. 
     This invention further relates to a a method of operating an internal combustion engine equipped with an exhaust gas after treatment device, said method comprising: 
     (A) operating said engine using a normally liquid or gaseous fuel; 
     (B) lubricating said engine using the foregoing low-sulfur consumable lubricating oil composition; 
     (C) removing part of said low-sulfur consumable lubricating oil composition from said engine, said removed part of said low-sulfur consumable lubricating oil composition (i) being combined with said fuel and consumed with said fuel as said engine is operated or (ii) being combined with the exhaust gas from said engine and removed from said engine with said exhaust gas; and 
     (D) adding an additional amount of said low-sulfur consumable lubricating oil composition to said engine to replace said removed part of said low-sulfur consumable lubricating oil composition.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/728,006 filed on Dec. 1, 2000 and a continuation-in-part ofU.S. application Ser. No. 09/664,834 filed Sep. 19, 2000.

TECHNICAL FIELD

This invention relates to low-sulfur consumable lubricating oilcompositions and to a method of operating an internal combustion engineusing the same. The inventive method provides the advantage of extendingrequired time intervals between oil changes and reducing NO_(x) levelsin exhaust gases.

BACKGROUND OF THE INVENTION

A problem associated with internal combustion engines equipped withexhaust gas aftertreatment devices (e.g., catalytic converters,particulate traps, catalyzed traps, etc.) is that the lubricating oilsfor such engines are used in both the crankcase as well as in high wearareas such as the valve train. Because these oils are used in high wearareas they usually contain extreme pressure (EP) agents which typicallycontain metal (e.g., zinc) and phosphorus in order to be effective.During the operation of the engine these EP agents decompose and theresulting decomposition products eventually enter the aftertreatmentdevice resulting in damage to the device. The problem therefore is toprovide a lubricating oil composition that avoids damaging the exhaustgas aftertreatment device.

Another problem associated with conventional internal combustion enginesis that the time interval required between oil changes typically is lessthan the time interval required for other service items such as airfilter replacements, coolant changes, brake replacements, and the like.Oil changes are viewed as one of the most aggravating and, in somecases, most costly maintenance aspects of vehicle ownership.Traditionally, oil change intervals have been extended by base stock andadditive upgrades. Since the 1920s, for example, the extensions havebeen about 15× or greater. Regardless of this progress, the timeintervals required between oil changes continue to lag behind the timeintervals required for other service items. The problem therefore is toimprove the lubricant technology for these engines so that the timeintervals between oil changes can be extended to coincide with otherservice intervals.

Another problem associated with the operation of internal combustionengines is that the exhaust gases from such engines contain NO_(x) whichis an undesirable pollutant. It would be advantageous if the level ofNO_(x) in the exhaust gases of internal combustion engines could bereduced.

The present invention provides a solution to each of these problems.With the present invention low-sulfur consumable lubricating oilcompositions characterized by the absence of EP agents containing metaland phosphorus are used and as a result the exhaust gas aftertreatmentdevice is protected from harmful exposure to such EP agents or theirdecomposition products. In accordance with the inventive method, therequired oil change intervals are extended due to the fact that duringoperation of the engine, used engine oil is continuously or periodicallyremoved from the engine and replaced with new oil. Unexpectedly, thelevels of NO_(x) in exhaust gases from engines operating in accordancewith the inventive method are reduced.

U.S. Pat. No. 5,955,403 discloses a sulfur free lubricating oilcomposition which comprises a major portion of a synthetic baselubricating oil and a minor portion of a tri(alkyl phenyl) phosphate ordi(alkylphenyl) phosphoric acid antiwear agent, an amine antioxidant asubstituted succinamide rust inhibitor, and a tolyltriazole. Thetri(alkylphenyl)phosphate antiwear agent is incorporated in the oil inan amount ranging between about 0.1 to 2.0 wt % and the amineantioxidant in amount ranging from about 0.1 to 5 wt %. The succinamideis present in an amount ranging from about 0.01 to 0.5 wt %, and thetolyltriazole from about 0.01 to 0.5 wt %.

U.S. Pat. No. 4,392,463 discloses a diesel engine having a firstlubrication system, containing conventional engine oil, used tolubricate that section of the engine subjected to excessive wear—thevalve train including the cam shaft, valve lifters, rocker arm, valvestems, etc., and a second lubricant system, utilizing diesel fuel, forlubricating the remaining section of the engine—the crankshaft andassociated parts, pistons, connecting rods, etc. By being exposed tocrankcase blowby exhaust gases, diesel fuel used to lubricate thecrankshaft, etc. absorbs pollutants and contaminants contained thereinand recirculates these contaminants through the fuel system to be burnedand exhausted. By constantly being lubricated with fresh lubricant, wearon these specific parts is reduced. The reference indicates thatfrequent lubrication changes have been eliminated because the dieselfuel/lubricant is continuously changed and circulated through the fuelsystem. Since the engine oil and the first lubrication system is notexposed to crankcase blowby exhausted gases, its useful life isprolonged, thus reducing the frequency of required oil changes.

SUMMARY OF THE INVENTION

This invention relates to a low-sulfur consumable lubricating oilcomposition, comprising: a base oil; an acylated nitrogen-containingcompound having a substituent of at least about 10 aliphatic carbonatoms; and a sulfur content of about 5 to about 250 ppm; saidcomposition being characterized by the absence of an extreme-pressureadditive containing metal and phosphorus.

This invention further relates to a a method of operating an internalcombustion engine equipped with an exhaust gas aftertreatment device,said method comprising:

(A) operating said engine using a normally liquid or gaseous fuel;

(B) lubricating said engine using the foregoing low-sulfur consumablelubricating oil composition;

(C) removing part of said low-sulfur consumable lubricating oilcomposition from said engine, said removed part of said low-sulfurconsumable lubricating oil composition (i) being combined with said fueland consumed with said fuel as said engine is operated or (ii) beingcombined with the exhaust gas from said engine and removed from saidengine with said exhaust gas; and

(D) adding an additional amount of said low-sulfur consumablelubricating oil composition to said engine to replace said removed partof said low-sulfur consumable lubricating oil composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an internal combustion engine thatis used in accordance with the inventive method, said engine beingequipped with an exhaust gas aftertreatment device.

FIG. 2 is a plot of NO_(x) levels in the exhaust gas generated in theengine test disclosed in Example 1 using a lubricating oil compositionwithin the scope of the invention having a sulfur content of 11 ppm.

FIG. 3 is a plot of NO_(x) levels in the exhaust gas generated in theengine test disclosed in Example 1 using a lubricating oil compositionoutside the scope of the invention having a sulfur content of 272 ppm.The engine test which resulted in the data plotted in FIG. 3 isdisclosed for purposes of comparison.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “low-sulfur” when used to refer to the inventive consumablelubricating oil composition means that the lubricating oil compositionhas a sulfur content in the range of about 5 ppm to about 250 ppm.

The term “consumable” when used to refer to the inventive lubricatingoil composition means that the oil composition may be either (i) mixedwith and consumed with the fuel composition used in the inventivemethod, or (ii) mixed with the exhaust gas produced during the operationof the inventive method and removed from the engine with the exhaust gasas the inventive method is performed.

The term “exhaust gas aftertreatment device” is used herein to refer toany device used in the exhaust gas system of an internal combustionengine to reduce pollutants in the exhaust gas. These include catalyticconverters, particulate traps, catalyzed traps, and the like.

The term “sulfur-free” when referring to additives or diluents for suchadditives used with the inventive low-sulfur consumable lubricating oilcomposition refers to a material that is free of elemental sulfur orcontains an impurity level of elemental sulfur not exceeding about 25ppm, and in one embodiment not exceeding about 15 ppm.

The term “hydrocarbyl” denotes a group having a carbon atom directlyattached to the remainder of the molecule and having a hydrocarbon orpredominantly hydrocarbon character within the context of thisinvention. Such groups include the following:

(1) Purely hydrocarbon groups; that is, aliphatic, (e.g., alkyl oralkenyl), alicyclic (e.g., cycloalkyl or cycloalkenyl), aromatic,aliphatic- and alicyclic-substituted aromatic, aromatic-substitutedaliphatic and alicyclic groups, and the like, as well as cyclic groupswherein the ring is completed through another portion of the molecule(that is, any two indicated substituents may together form an alicyclicgroup). Such groups are known to those skilled in the art. Examplesinclude methyl, ethyl, octyl, decyl, octadecyl, cyclohexyl, phenyl, etc.

(2) Substituted hydrocarbon groups; that is, groups containingnon-hydrocarbon substituents which do not alter the predominantlyhydrocarbon character of the group. Those skilled in the art will beaware of suitable substituents. Examples include hydroxy, nitro, cyano,alkoxy, acyl, etc.

(3) Hetero groups; that is, groups which, while predominantlyhydrocarbon in character, contain atoms other than carbon in a chain orring otherwise composed of carbon atoms. Suitable hetero atoms will beapparent to those skilled in the art and include, for example, nitrogenor oxygen.

In general, no more than about three substituents or hetero atoms, andpreferably no more than one, will be present for each 10 carbon atoms inthe hydrocarbyl group.

Terms such as “alkyl-based,” “aryl-based,” and the like have meaningsanalogous to the above with respect to alkyl groups, aryl groups and thelike.

The term “hydrocarbon-based” has the same meaning and can be usedinterchangeably with the term hydrocarbyl when referring to moleculargroups having a carbon atom attached directly to the remainder of amolecule.

The term “lower” as used herein in conjunction with terms such ashydrocarbyl, alkyl, alkenyl, alkoxy, and the like, is intended todescribe such groups which contain a total of up to 7 carbon atoms.

The term “oil-soluble” refers to a material that is soluble in mineraloil to the extent of at least about one gram per liter at 25° C.

The Low-Sulfur Consumable Lubricating Oil Composition

The low-sulfur consumable lubricating oil composition, in oneembodiment, may be comprised of components that add only C, H, O or N tothe lubricating oil composition. In one embodiment, Si may be present.Excluding sulfur, as discussed below, any other elements that may bepresent are present as impurities and as such are at relatively lowconcentrations. The concentration of each of these impurities (prior touse of the oil in the engine) is typically less than about 500 ppm, andin one embodiment less than about 250 ppm, and in one embodiment lessthan about 100 ppm, and in one embodiment less than about 50 ppm, and inone embodiment less than about 25 ppm, and in one embodiment less thanabout 10 ppm. This lubricating oil composition is characterized by theabsence of EP additives comprised of metal (e.g., zinc) and phosphorus.In one embodiment, this lubricating oil composition is characterized bythe absence of detergents or dispersants of the ash-producing type.

The sulfur in the inventive lubricating oil composition may be in anyform. The sulfur may be elemental sulfur or it may present in thelubricating oil composition or added to the lubricating oil compositionas part of a sulfur-containing compound. The sulfur-containing compoundmay be an inorganic sulfur compound or an organic sulfur compound. Thesulfur-containing compound may be a compound containing one or more ofthe groups: sulfamoyl, sulfenamoyl, sulfeno, sulfido, sulfinamoyl,sulfino, sulfinyl, sulfo, sulfonio, sulfonyl, sulfonyldioxy, sulfate,thio, thiocarbamoyl, thiocarbonyl, thiocarbonylamino, thiocarboxy,thiocyanato, thioformyl, thioxo, thioketone, thioaldehyde, thioester,and the like. The sulfur may be present in a hetero group or compoundwhich contains carbon atoms and sulfur atoms (and, optionally, otherhetero atoms such as oxygen or nitrogen) in a chain or ring. Thesulfur-containing compound may be a sulfur oxide such as sulfur dioxideor sulfur trioxide. The sulfur or sulfur-containing compound may beintentionally added to the inventive lubricating oil composition, or itmay be present in the base oil or in one or more of the additives forthe inventive lubricating oil composition as an impurity. The sulfurcontent in the inventive lubricating oil composition is critical and isin the range of about 5 to about 250 ppm, and in one embodiment about 5to about 200 ppm, and in one embodiment about 5 to about 150 ppm, and inone embodiment about 5 to about 100 ppm, and in one embodiment about 5to about 50 ppm, and in one embodiment about 5 to about 25 ppm, and inone embodiment about 5 to about 15 ppm, as measured by inductivelycoupled plasma (ICP) or x-ray techniques.

The low-sulfur consumable lubricating oil composition is comprised ofone or more base oils which are generally present in a major amount(i.e. an amount greater than about 50% by weight). Generally, the baseoil is present in an amount greater than about 60%, or greater thanabout 70%, or greater than about 80% by weight of the lubricating oilcomposition.

The low-sulfur consumable lubricating oil composition may have aviscosity of up to about 16.3 cSt at 100° C., and in one embodimentabout 5 to about 16.3 cSt at 100° C., and in one embodiment about 6 toabout 13 cSt at 100° C. In one embodiment, the lubricating oilcomposition has an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40,0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20,10W-30, 10W-40 OR 10W-50.

The low-sulfur consumable lubricating oil composition may have ahigh-temperature/high-shear viscosity at 150° C. as measured by theprocedure in ASTM D4683 of up to about 4 centipoise, and in oneembodiment up to about 3.7 centipoise, and in one embodiment about 2 toabout 4 centipoise, and in one embodiment about 2.2 to about 3.7centipoise, and in one embodiment about 2.7 to about 3.5 centipoise.

The base oil used in the low-sulfur consumable lubricating oilcomposition may be a natural oil, synthetic oil or mixture thereof,provided the sulfur content of such oil does not exceed theabove-indicated sulfur concentration limit required for the inventivelow-sulfur lubricating oil composition. The natural oils that are usefulinclude animal oils and vegetable oils (e.g., castor oil, lard oil) aswell as mineral lubricating oils such as liquid petroleum oils andsolvent treated or acid-treated mineral lubricating oils of theparaffinic, naphthenic or mixed paraffinic-naphthenic types. Oilsderived from coal or shale are also useful. Synthetic lubricating oilsinclude hydrocarbon oils such as polymerized and interpolymerizedolefins (e.g., polybutylenes, polypropylenes, propylene isobutylenecopolymers, etc.); poly(1-hexenes), poly-(1-octenes), poly(1-decenes),etc. and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.);alkylated diphenyl ethers and the derivatives, analogs and homologsthereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils that can be used. These are exemplified by the oilsprepared through polymerization of ethylene oxide or propylene oxide,the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g.,methyl-polyisopropylene glycol ether having an average molecular weightof about 1000, diphenyl ether of polyethylene glycol having a molecularweight of about 500-1000, diethyl ether of polypropylene glycol having amolecular weight of about 1000-1500, etc.) or mono- and polycarboxylicesters thereof, for example, the acetic acid esters, mixed C₃₋₈ fattyacid esters, or the C₁₃Oxo acid diester of tetraethylene glycol.

Another suitable class of synthetic lubricating oils that can be usedcomprises the esters of dicarboxylic acids (e.g., phthalic acid,succinic acid, alkyl succinic acids, alkenyl succinic acids, maleicacid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipicacid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenylmalonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol,hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,diethylene glycol monoether, propylene glycol, etc.) Specific examplesof these esters include dibutyl adipate, di(2-ethylhexyl) sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol ethers such as neopentylglycol, trimethylol propane, pentaerythritol, dipentaerythritol,tripentaerythritol, etc.

The oil can be a poly-alpha-olefin (PAO). Typically, the PAOs arederived from monomers having from about 4 to about 30, or from about 4to about 20, or from about 6 to about 16 carbon atoms. Examples ofuseful PAOs include those derived from octene, decene, mixtures thereof,and the like. These PAOs may have a viscosity from about 2 to about 15,or from about 3 to about 12, or from about 4 to about 8 cSt at 100° C.Examples of useful PAOs include 4 cSt at 100° C. poly-alpha-olefins, 6cSt at 100° C. poly-alpha-olefins, and mixtures thereof. Mixtures ofmineral oil with one or more of the foregoing PAOs may be used.

Unrefined, refined and rerefined oils, either natural or synthetic (aswell as mixtures of two or more of any of these) of the type disclosedhereinabove can be used in the lubricants of the present invention.Unrefined oils are those obtained directly from a natural or syntheticsource without further purification treatment. For example, a shale oilobtained directly from retorting operations, a petroleum oil obtaineddirectly from primary distillation or ester oil obtained directly froman esterification process and used without further treatment would be anunrefined oil. Refined oils are similar to the unrefined oils exceptthey have been further treated in one or more purification steps toimprove one or more properties. Many such purification techniques areknown to those skilled in the art such as solvent extraction, secondarydistillation, acid or base extraction, filtration, percolation, etc.Rerefined oils are obtained by processes similar to those used to obtainrefined oils applied to refined oils which have been already used inservice. Such rerefined oils are also known as reclaimed or reprocessedoils and often are additionally processed by techniques directed toremoval of spent additives and oil breakdown products.

The acylated nitrogen-containing compound used in the inventivelow-sulfur consumable lubricating oil composition typically functions asan ashless dispersant. A number of acylated nitrogen-containingcompounds having a substituent of at least about 10 aliphatic carbonatoms and made by reacting a carboxylic acid acylating agent with anamino compound are known to those skilled in the art. In such compoundsthe acylating agent is linked to the amino compound through an imido,amido, amidine or salt linkage. The substituent of at least about 10aliphatic carbon atoms may be in either the carboxylic acid acylatingagent derived portion of the molecule or in the amino compound derivedportion of the molecule. In one embodiment, it is in the acylating agentportion. The acylating agent can vary from formic acid and its acylderivatives to acylating agents having high molecular weight aliphaticsubstituents of up to about 5,000, 10,000 or 20,000 carbon atoms. Theamino compounds are characterized by the presence within their structureof at least one HN<group.

In one embodiment, the acylating agent is a mono- or polycarboxylic acid(or reactive equivalent thereof) such as a substituted succinic orpropionic acid and the amino compound is a polyamine or mixture ofpolyamines, most typically, a mixture of ethylene polyamines. The aminealso may be a hydroxyalkyl-substituted polyamine. The aliphaticsubstituent in such acylating agents typically averages at least about30 or at least about 50 and up to about 400 carbon atoms.

Illustrative hydrocarbon based groups containing at least 10 carbonatoms are n-decyl, n-dodecyl, tetrapropylene, n-octadecyl, oleyl,chlorooctadecyl, triicontanyl, etc. Generally, the hydrocarbon-basedsubstituents are made from homo- or interpolymers (e.g., copolymers,terpolymers) of mono- and di-olefins having 2 to 10 carbon atoms, suchas ethylene, propylene, 1-butene, isobutene, butadiene, isoprene,1-hexene, 1-octene, etc. Typically, these olefins are 1-monoolefins. Thesubstituent can also be derived from the halogenated (e.g., chlorinatedor brominated) analogs of such homo- or interpolymers. The substituentcan, however, be made from other sources, such as monomeric highmolecular weight alkenes (e.g., 1-tetracontene) and chlorinated analogsand hydrochlorinated analogs thereof, aliphatic petroleum fractions,particularly paraffin waxes and cracked and chlorinated analogs andhydrochlorinated analogs thereof, white oils, synthetic alkenes such asthose produced by the Ziegler-Natta process (e.g., poly(ethylene)greases) and other sources known to those skilled in the art. Anyunsaturation in the substituent may be reduced or eliminated byhydrogenation according to procedures known in the art.

The hydrocarbon-based substituents are substantially saturated, that is,they contain no more than one carbon-to-carbon unsaturated bond forevery ten carbon-to-carbon single bonds present. Usually, they containno more than one carbon-to-carbon non-aromatic unsaturated bond forevery 50 carbon-to-carbon bonds present.

The hydrocarbon-based substituents are also substantially aliphatic innature, that is, they contain no more than one non-aliphatic moiety(cycloalkyl, cycloalkenyl or aromatic) group of 6 or less carbon atomsfor every 10 carbon atoms in the substituent. Usually, however, thesubstituents contain no more than one such non-aliphatic group for every50 carbon atoms, and in many cases, they contain no such non-aliphaticgroups at all; that is, the typical substituents are purely aliphatic.Typically, these purely aliphatic substituents are alkyl or alkenylgroups.

Specific examples of the substantially saturated hydrocarbon-basedsubstituents containing an average of more than about 30 carbon atomsare the following:

a mixture of poly(ethylene/propylene) groups of about 35 to about 70carbon atoms;

a mixture of the oxidatively or mechanically degradedpoly(ethylene/propylene) groups of about 35 to about 70 carbon atoms;

a mixture of poly(propylene/1-hexene) groups of about 80 to about 150carbon atoms;

a mixture of poly(isobutene) groups having an average of about 50 toabout 200 carbon atoms.

A useful source of the substituents are poly(isobutene)s obtained bypolymerization of a C₄ refinery stream having a butene content of about35 to about 75 weight percent and isobutene content of about 30 to about60 weight percent in the presence of a Lewis acid catalyst such asaluminum trichloride or boron trifluoride. These polybutenes containpredominantly (greater than 80% of total repeating units) isobutenerepeating units of the configuration

In one embodiment, the substituent is a polyisobutene group derived froma polyisobutene having a high methylvinylidene isomer content, that is,at least about 70% methylvinylidene, and in one embodiment at leastabout 80% methylvinylidene. Suitable high methylvinylidenepolyisobutenes include those prepared using boron trifluoride catalysts.The preparation of such polyisobutenes in which the methylvinylideneisomer comprises a high percentage of the total olefin composition isdescribed in U.S. Pat. Nos. 4,152,499 and 4,605,808, the disclosures ofeach of which are incorporated herein by reference.

In one embodiment, the carboxylic acid acylating agent is a hydrocarbonsubstituted succinic acid or anhydride. The substituted succinic acid oranhydride consists of hydrocarbon-based substituent groups and succinicgroups wherein the substituent groups are derived from a polyalkene,said acid or anhydride being characterized by the presence within itsstructure of an average of at least about 0.9 succinic group for eachequivalent weight of substituent groups, and in one embodiment about 0.9to about 2.5 succinic groups for each equivalent weight of substituentgroups. The polyalkene generally has a number average molecular weight({overscore (M)}n) of at least about 700, and in one embodiment about700 to about 2000, and in one embodiment about 900 to about 1800. Theratio between the weight average molecular weight ({overscore (M)}w) andthe ({overscore (M)}n) (that is, the {overscore (M)}w/{overscore (M)}n)can range from about 1 to about 10, or about 1.5 to about 5. In oneembodiment the polyalkene has an {overscore (M)}w/{overscore (M)}n valueof about 2.5 to about 5. For purposes of this invention, the number ofequivalent weights of substituent groups is deemed to be the numbercorresponding to the quotient obtained by dividing the {overscore (M)}nvalue of the polyalkene from which the substituent is derived into thetotal weight of the substituent groups present in the substitutedsuccinic acid. Thus, if a substituted succinic acid is characterized bya total weight of substituent group of 40,000 and the {overscore (M)}nvalue for the polyalkene from which the substituent groups are derivedis 2000, then that substituted succinic acylating agent is characterizedby a total of 20 (40,000/2000=20) equivalent weights of substituentgroups.

In one embodiment the carboxylic acid acylating agent is a substitutedsuccinic acid or anhydride, said substituted succinic acid or anhydrideconsisting of hydrocarbon-based substituent groups and succinic groupswherein the substituent groups are derived from polybutene in which atleast about 50% of the total units derived from butenes is derived fromisobutylene. The polybutene is characterized by an {overscore (M)}nvalue of about 1500 to about 2000 and an {overscore (M)}w/{overscore(M)}n value of about 3 to about 4. These acids or anhydrides arecharacterized by the presence within their structure of an average ofabout 1.5 to about 2.5 succinic groups for each equivalent weight ofsubstituent groups.

In one embodiment the carboxylic acid is at least one substitutedsuccinic acid or anhydride, said substituted succinic acid or anhydrideconsisting of substituent groups and succinic groups wherein thesubstituent groups are derived from polybutene in which at least about50% of the total units derived from butenes is derived from isobutylene.The polybutene has an {overscore (M)}n value of about 800 to about 1200and an {overscore (M)}w/{overscore (M)}n value of about 2 to about 3.The acids or anhydrides are characterized by the presence within theirstructure of an average of about 0.9 to about 1.2 succinic groups foreach equivalent weight of substituent groups.

The amino compound is characterized by the presence within its structureof at least one HN<group and can be a monoamine or polyamine. Mixturesof two or more amino compounds can be used in the reaction with one ormore acylating reagents. In one embodiment, the amino compound containsat least one primary amino group (i.e., —NH₂) and more preferably theamine is a polyamine, especially a polyamine containing at least two—NH— groups, either or both of which are primary or secondary amines.The amines may be aliphatic, cycloaliphatic, aromatic or heterocyclicamines.

Among the useful amines are the alkylene polyamines, including thepolyalkylene polyamines. The alkylene polyamines include thoseconforming to the formula

wherein n is from 1 to about 10; each R is independently a hydrogenatom, a hydrocarbyl group or a hydroxy-substituted or amine-substitutedhydrocarbyl group having up to about 30 atoms, or two R groups ondifferent nitrogen atoms can be joined together to form a U group, withthe proviso that at least one R group is a hydrogen atom and U is analkylene group of about 2 to about 10 carbon atoms. U may be ethylene orpropylene. Alkylene polyamines where each R is hydrogen or anamino-substituted hydrocarbyl group with the ethylene polyamines andmixtures of ethylene polyamines are useful. Usually n will have anaverage value of from about 2 to about 7. Such alkylene polyaminesinclude methylene polyamine, ethylene polyamines, propylene polyamines,butylene polyamines, pentylene polyamines, hexylene polyamines,heptylene polyamines, etc. The higher homologs of such amines andrelated amino alkyl-substituted piperazines are also included.

Alkylene polyamines that are useful include ethylene diamine,triethylene tetramine, propylene diamine, trimethylene diamine,hexamethylene diamine, decamethylene diamine, octamethylene diamine,di(heptamethylene) triamine, tripropylene tetramine, tetraethylenepentamine, trimethylene diamine, pentaethylene hexamine,di(trimethylene)triamine, N-(2-aminoethyl)piperazine,1,4-bis(2-aminoethyl)piperazine, and the like. Higher homologs as areobtained by condensing two or more of the above-illustrated alkyleneamines are useful, as are mixtures of two or more of any of theafore-described polyamines.

Ethylene polyamines, such as those mentioned above, are especiallyuseful for reasons of cost and effectiveness. Such polyamines aredescribed in detail under the heading “Diamines and Higher Amines” inThe Encyclopedia of Chemical Technology, Second Edition, Kirk andOthmer, Volume 7, pages 27-39, Interscience Publishers, Division of JohnWiley and Sons, 1965, which is hereby incorporated by reference for thedisclosure of useful polyamines. Such compounds are prepared mostconveniently by the reaction of an alkylene chloride with ammonia or byreaction of an ethylene imine with a ring-opening reagent such asammonia, etc. These reactions result in the production of the somewhatcomplex mixtures of alkylene polyamines, including cyclic condensationproducts such as piperazines.

Other useful types of polyamine mixtures are those resulting fromstripping of the above-described polyamine mixtures. In this instance,lower molecular weight polyamines and volatile contaminants are removedfrom an alkylene polyamine mixture to leave as residue what is oftentermed “polyamine bottoms”. In general, alkylene polyamine bottoms canbe characterized as having less than about 2% by weight, usually lessthan about 1% by weight material boiling below about 200° C. In theinstance of ethylene polyamine bottoms, which are readily available andfound to be quite useful, the bottoms contain less than about 2% byweight total diethylene triamine (DETA) or triethylene tetramine (TETA).A typical sample of such ethylene polyamine bottoms obtained from theDow Chemical Company of Freeport, Tex. designated “E-100” showed aspecific gravity at 15.6° C. of 1.0168, a percent nitrogen by weight of33.15 and a viscosity at 40° C. of 121 centistokes. Gas chromatographyanalysis of such a sample indicates it contains about 0.93% “Light Ends”(most probably DETA), 0.72% TETA, 21.74% tetraethylene pentamine and76.61% pentaethylene hexamine and higher (by weight). These alkylenepolyamine bottoms include cyclic condensation products such aspiperazine and higher analogs of diethylenetriamine,triethylenetetramine and the like.

These alkylene polyamine bottoms can be reacted solely with theacylating agent, in which case the amino reactant consists essentiallyof alkylene polyamine bottoms, or they can be used with other amines andpolyamines, or alcohols or mixtures thereof. In these latter cases atleast one amino reactant comprises alkylene polyamine bottoms.

Other polyamines are described in, for example, U.S. Pat. Nos. 3,219,666and 4,234,435, and these patents are hereby incorporated by referencefor their disclosures of amines which can be reacted with the acylatingagents described above to form useful acylated nitrogen-containingcompounds.

In one embodiment, the amine may be a hydroxyamine. Typically, thehydroxyamines are primary, secondary or tertiary alkanol amines ormixtures thereof. Such amines can be represented by the formulae:

H₂N—R′—OH RN(H)—R′—OH RRN—R′—OH

wherein each R is independently a hydrocarbyl group of one to abouteight carbon atoms or hydroxyhydrocarbyl group of two to about eightcarbon atoms, preferably one to about four, and R′ is a divalenthydrocarbyl group of about two to about 18 carbon atoms, preferably twoto about four. The group —R′—OH in such formulae represents thehydroxyhydrocarbyl group. R′ can be an acyclic, alicyclic or aromaticgroup. Typically, R′ is an acyclic straight or branched alkylene groupsuch as an ethylene, 1,2-propylene, 1,2-butylene, 1,2-octadecylene, etc.group. Where two R groups are present in the same molecule they can bejoined by a direct carbon-to-carbon bond or through a heteroatom (e.g.,oxygen or nitrogen) to form a 5-, 6-, 7- or 8-membered ring structure.Examples of such heterocyclic amines include N-(hydroxyl loweralkyl)-morpholines, -piperidines, -oxazolidines, and the like.Typically, however, each R′ is independently a methyl, ethyl, propyl,butyl, pentyl or hexyl group.

Examples of these alkanolamines include mono-, di-, and triethanolamine, diethylethanolamine, ethylethanolamine, butyldiethanolamine, etc.

The hydroxyamines can also be an ether N-(hydroxyhydrocarbyl)-amine.These are hydroxypoly(hydrocarbyloxy) analogs of the above-describedhydroxy amines (these analogs also include hydroxyl-substitutedoxyalkylene analogs). Such N-(hydroxyhydrocarbyl) amines can beconveniently prepared by reaction of epoxides with afore-describedamines and can be represented by the formulae:

N₂N—(R′O)_(x)—H RN(H)—(R′O)_(x)H RRN—(R′O)_(x)H

wherein x is a number from about 2 to about 15 and R and R′ are asdescribed above. R may also be a hydroxypoly(hydrocarbyloxy) group.

The acylated nitrogen-containing compounds include amine salts, amides,imides, amidines, amidic acids, amidic salts and imidazolines as well asmixtures thereof. To prepare the acylated nitrogen-containing compoundsfrom the acylating reagents and the amino compounds, one or moreacylating reagents and one or more amino compounds are heated,optionally in the presence of a normally liquid, substantially inertorganic liquid solvent/diluent, at temperatures in the range of about80° C. up to the decomposition point of either the reactants or thecarboxylic derivative but normally at temperatures in the range of about100° C. up to about 300° C. provided 300° C. does not exceed thedecomposition point. Temperatures of about 125° C. to about 250° C. arenormally used. The acylating reagent and the amino compound are reactedin amounts sufficient to provide from about one-half equivalent up toabout 2 moles of amino compound per equivalent of acylating reagent.

Many patents have described useful acylated nitrogen-containingcompounds including U.S. Pat. Nos. 3,172,892; 3,219,666; 3,272,746;3,310,492; 3,341,542; 3,444,170; 3,455,831; 3,455,832; 3,576,743;3,630,904; 3,632,511; 3,804,763; and 4,234,435. A typical acylatednitrogen-containing compound of this class is that made by reacting apoly(isobutene)-substituted succinic acid acylating agent (e.g.,anhydride, acid, ester, etc.) wherein the poly(isobutene) substituenthas between about 50 to about 400 carbon atoms with a mixture ofethylenepolyamines having about 3 to about 7 amino nitrogen atoms perethylenepolyamine and about 1 to about 6 ethylene units. The above-notedU.S. patents are hereby incorporated by reference for their disclosureof acylated amino compounds and their method of preparation.

Another type of acylated nitrogen-containing compound belonging to thisclass is that made by reacting a carboxylic acid acylating agent with apolyamine, wherein the polyamine is the product made by condensing ahydroxy material with an amine. These compounds are described in U.S.Pat. No. 5,053,152 which is incorporated herein by reference for itsdisclosure of such compounds.

Another type of acylated nitrogen-containing compound belonging to thisclass is that made by reacting the afore-described alkyleneamines withthe afore-described substituted succinic acids or anhydrides andaliphatic monocarboxylic acids having from 2 to about 22 carbon atoms.In these types of acylated nitrogen compounds, the mole ratio ofsuccinic acid to monocarboxylic acid ranges from about 1:0.1 to about1:1. Typical of the monocarboxylic acid are formic acid, acetic acid,dodecanoic acid, butanoic acid, oleic acid, stearic acid, the commercialmixture of stearic acid isomers known as isostearic acid, tall oil acid,etc. Such materials are more fully described in U.S. Pat. Nos. 3,216,936and 3,250,715 which are hereby incorporated by reference for theirdisclosures in this regard.

Still another type of acylated nitrogen-containing compound that may beuseful is the product of the reaction of a fatty monocarboxylic acid ofabout 12-30 carbon atoms and the afore-described alkyleneamines,typically, ethylene-, propylene- or trimethylenepolyamines containing 2to 8 amino groups and mixtures thereof. The fatty monocarboxylic acidsare generally mixtures of straight and branched chain fatty carboxylicacids containing 12-30 carbon atoms. A widely used type of acylatednitrogen compound is made by reacting the afore-describedalkylenepolyamines with a mixture of fatty acids having from 5 to about30 mole percent straight chain acid and about 70 to about 95% molebranched chain fatty acids. Among the commercially available mixturesare those known widely in the trade as isostearic acid. These mixturesare produced as a by-product from the dimerization of unsaturated fattyacids as described in U.S. Pat. Nos. 2,812,342 and 3,260,671.

The branched chain fatty acids can also include those in which thebranch is not alkyl in nature, such as found in phenyl and cyclohexylstearic acid and the chloro-stearic acids. Branched chain fattycarboxylic acid/alkylene polyamine products have been describedextensively in the art. See for example, U.S. Pat. Nos. 3,110,673;3,251,853; 3,326,801; 3,337,459; 3,405,064; 3,429,674; 3,468,639;3,857,791. These patents are hereby incorporated by reference for theirdisclosure of fatty acid/polyamine condensates for use in lubricatingoil formulations.

In one embodiment, the inventive low-sulfur consumable lubricating oilcomposition is characterized by a chlorine level of no more than about10 ppm, and in one embodiment no more than about 7 ppm, and in oneembodiment no more than about 5 ppm. This necessitates that the acylatednitrogen-containing compound be chlorine-free or contain such lowchlorine levels that the addition of such compound to the lubricatingoil composition results in the formation of a lubricating oilcomposition with a chlorine level of no more than about 10 ppm. In oneembodiment, the acylated nitrogen-containing compound has a chlorinecontent of no more than about 50 ppm, and in one embodiment no more thanabout 25 ppm, and in one embodiment no more than about 10 ppm. In oneembodiment, the acylated nitrogen-containing compound is chlorine free.

The acylated nitrogen-containing compound is typically employed in thelow-sulfur consumable lubricating oil composition at a concentration inthe range of about 1% to about 25% percent by weight, and in oneembodiment about 5% to about 15% by weight. These compounds can be addeddirectly to the lubricating oil composition. In one embodiment, however,they are diluted with a substantially inert, normally liquid organicdiluent such as mineral oil, naphtha, benzene, toluene or xylene to forman additive concentrate. These concentrates usually contain from about1% to about 99% by weight, and in one embodiment about 10% to about 90%by weight of the diluent. In one embodiment, the organic diluent is asulfur-free composition.

An advantage of the inventive low-sulfur consumable lubricating oilcompositions is that these oil compositions may be easier to dispose offrom an environmental perspective than conventional lubricating oils.This is due to the absence of EP additives containing phosphorus andmetal in these lubricating oil compositions. Conventional lubricatingoil compositions, on the other hand, typically contain relatively highconcentrations of such EP additives.

The low-sulfur consumable lubricating oil composition may contain, inaddition to the base oil, sulfur and acylated nitrogen-containingcompounds referred to above, one or more detergents or dispersants ofthe ashless type. The ashless detergents and dispersants are so calleddespite the fact that, depending on their constitution, they may uponcombustion yield a non-volatile material such as boric oxide; however,they do not ordinarily contain metal and therefore do not yield ametal-containing ash on combustion. Many types are known in the art, andare suitable for use in these lubricating oil compositions. Theseinclude the following:

(1) Reaction products of carboxylic acids (or derivatives thereof)containing at least about 34, and in one embodiment at least about 54carbon atoms, with organic hydroxy compounds such as phenols andalcohols, and/or basic inorganic materials. Examples of these“carboxylic dispersants” are described in many U.S. Patents includingU.S. Pat. Nos. 3,219,666; 4,234,435; and 4,938,881.

(2) Reaction products of relatively high molecular weight aliphatic oralicyclic halides with amines, preferably oxyalkylene polyamines. Thesemay be characterized as “amine dispersants” and examples thereof aredescribed for example, in the following U.S. Patents: U.S. Pat. Nos.3,275,554; 3,438,757; 3,454,555; and 3,565,804.

(3) Reaction products of alkyl phenols in which the alkyl group containsat least about 30 carbon atoms with aldehydes (especially formaldehyde)and amines (especially polyalkylene polyamines), which may becharacterized as “Mannich dispersants.” The materials described in thefollowing U.S. Patents are illustrative: U.S. Pat. Nos. 3,649,229;3,697,574; 3,725,277; 3,725,480; 3,726,882; and 3,980,569.

(4) Products obtained by post-treating the amine or Mannich dispersantswith such reagents as urea, aldehydes, ketones, carboxylic acids,hydrocarbon-substituted succinic anhydrides, nitrites, epoxides, boroncompounds, phosphorus compounds or the like. Exemplary materials of thiskind are described in the following U.S. Patents: U.S. Pat. Nos.3,639,242; 3,649,229; 3,649,659; 3,658,836; 3,697,574; 3,702,757;3,703,536; 3,704,308; and 3,708,422.

(5) Interpolymers of oil-solubilizing monomers such as decylmethacrylate, vinyl decyl ether and high molecular weight olefins withmonomers containing polar substituents, e.g., aminoalkyl acrylates oracrylamides and poly-(oxyethylene)-substituted acrylates. These may becharacterized as “polymeric dispersants” and examples thereof aredisclosed in the following U.S. Patents: U.S. Pat. Nos. 3,329,658;3,449,250; 3,519,565; 3,666,730; 3,687,849; and 3,702,300.

The above-noted patents are incorporated by reference herein for theirdisclosures of ashless dispersants.

The low-sulfur consumable lubricating oil composition may also containother lubricant additives known in the art. These include, for example,corrosion-inhibiting agents, antioxidants, viscosity modifiers, pourpoint depressants, friction modifiers, fluidity modifiers, anti-foamagents, etc.

Pour point depressants are used to improve the low temperatureproperties of oil-based compositions. See, for example, page 8 of“Lubricant Additives” by C. V. Smalheer and R. Kennedy Smith (LeziusHiles Co. publishers, Cleveland, Ohio, 1967). Examples of useful pourpoint depressants are polymethacrylates; polyacrylates; polyacrylamides;condensation products of haloparaffin waxes and aromatic compounds;vinyl carboxylate polymers; and terpolymers of dialkylfumarates, vinylesters of fatty acids and alkyl vinyl ethers. Pour point depressants aredescribed in U.S. Pat. Nos. 2,387,501; 2,015,748; 2,655,479; 1,815,022;2,191,498; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 which areherein incorporated by reference for their relevant disclosures.

Anti-foam agents are used to reduce or prevent the formation of stablefoam. Typical anti-foam agents include silicones or organic polymers.Additional antifoam compositions are described in “Foam Control Agents,”by Henry T. Kerner (Noyes Data Corporation, 1976), pages 125-162.

Each of the foregoing additives, when used, is used at a functionallyeffective amount to impart the desired properties to the lubricant.Thus, for example, if an additive is a corrosion inhibitor, afunctionally effective amount of this corrosion inhibitor would be anamount sufficient to impart the desired corrosion inhibitioncharacteristics to the lubricant. Generally, the concentration of eachof these additives, when used, ranges from about 0.001% to about 20% byweight, and in one embodiment about 0.01% to about 10% by weight basedon the total weight of the low-sulfur consumable lubricating oilcomposition.

These additives can be added directly to the low-sulfur consumablelubricating oil composition. In one embodiment, however, they arediluted with a substantially inert, normally liquid organic diluent suchas mineral oil, naphtha, benzene, toluene or xylene to form an additiveconcentrate. These concentrates usually contain from about 1% to about99% by weight, and in one embodiment about 10% to about 90% by weight ofsuch diluent. In one embodiment, this diluent is a sulfur-freecomposition.

Method of Operating Internal Combustion Engine

The inventive method will be initially discussed with reference to FIG.1. The engine 10 may be a spark ignition internal combustion engine,which may be referred to as a gasoline powered engine, or compressionignition internal combustion engine, which may be referred to as adiesel engine. The spark ignition engine may be a four-stroke internalcombustion engine.

The engine 10 may employ a split lubrication system where the high-wearareas or components of the engine are lubricated using a conventionallubricating oil composition, and the crankcase is lubricated using theinventive low-sulfur consumable lubricating oil composition. Thehigh-wear areas lubricated using a conventional lubricating oilcomposition include the valve train (including the cam shaft andassociated parts such as cam lobes, tappets, followers, valve tips,rocker arms, rocker arm mechanisms, and the like). The crankcaselubricated using the inventive low-sulfur consumable lubricating oilcomposition may include the crankshaft and associated parts, pistons,connecting rods, and the like. Engines employing split lubricationsystems of this type are disclosed in U.S. Pat. Nos. 4,392,463;5,195,474; and 5,709,186; and French Patent 2,605,677. These patents areincorporated herein by reference for their disclosure of enginesemploying split lubrication systems.

The engine 10 may be lubricated in the high-wear areas using a solidfilm lubricant and in the remaining areas using the inventive low-sulfurconsumable lubricating oil composition. The high-wear areas may belubricated using a combination of a solid film lubricant and theinventive low-sulfur consumable lubricating oil composition. The solidfilm lubricant may be any solid film lubricant that provides enhancedwear resistance characteristics and enhanced lubricity characteristicswhen applied to wear interfaces or contacts as compared to when thesolid film lubricant is not present. The solid film lubricant may have afilm thickness of about 5 to about 100 microns, and in one embodimentabout 5 to about 75 microns. The solid film lubricant may be applied tothe desired engine components by the engine manufacturer. Among the highwear areas or components of the engines that may be so lubricated arewear interfaces or contacts in the valve train. These include the wearinterfaces or contacts of the cam lobes, tappets, followers, valve tips,rocker arms, rocker arm mechanisms, and the like. Additional enginecomponents that may be lubricated in this manner include the wearinterfaces or contacts of the cylinder bores, cylinder walls, pistonrings, skirts, bearings, connecting rods, and the like. Included amongthe solid film lubricants that may be used are those disclosed in U.S.Pat. No. 5,482,637 which discloses solid film lubricants comprised of atleast two solid lubricants selected from graphite, MoS₂, and BN. U.S.Pat. No. 5,358,753 discloses solid film lubricants comprised of graphiteand MoS₂. International Publication WO 97/13884 discloses a compositecoating of a metal and an oxide of the metal wherein the oxide has alower oxygen content than any of the metal's oxide forms, the metalbeing selected from Ni, Cu, Mo, Fe or an alloy thereof. German Patent DE195 48 718 C1 discloses solid film lubricants comprised of a metal oxidecoating wherein the metal is Ti, Al, Mo, V or Cr. The solid filmlubricant may be a carbon coating that is applied under vacuum by alaser. The foregoing patents are incorporated herein by reference fortheir disclosures of solid film lubricants.

The engine 10 may be a camless internal combustion engine. Camlessinternal combustion engines do not employ a camshaft for controlling thetiming and lifting of the engine's intake and exhaust valves. Theseengines typically employ intake valves and exhaust valves that areelectrically actuated, hydraulically actuated or electrohydraulicallyactuated. Examples of such engines are disclosed in U.S. Pat. Nos.5,255,641; 5,311,711; 5,367,990; 5,373,817; 5,377,631; 5,404,844;5,419,301; 5,456,221; 5,456,222, 5,562,070; 5,572,961; 5,615,646;5,619,965; 5,694,893; 5,709,178; 5,758,625; 5,970,956; and 6,024,060,which are incorporated by reference for their disclosures of camlessengines.

The engine 10 includes a crankcase 12, and a fuel system 14, whichincludes a fuel tank, fuel pump, fuel injectors, fuel filter, and thelike. The fuel mixes with air, and undergoes combustion in thecombustion chambers of the engine. An exhaust gas is removed from theengine as indicated by arrow 16. An exhaust gas aftertreatment device 18(e.g., catalytic converter, particulate trap, catalyzed trap, and thelike) and an exhaust muffler 20 are provided as part of an exhaustsystem for removing exhaust gas from the engine. The engine 10 includesa pump (not shown) for circulating oil throughout the engine and an oilsump 22. The engine 10 is equipped with a make-up oil reservoir 24 and apump or metering device 26 for advancing new oil from the make-up oilreservoir 24 to the crankcase 12.

The engine 10 operates in the normal sequence with the fuel beingadvanced from the fuel system 14 to the combustion chambers of theengine where a mixture of the fuel and air undergoes combustion. Theexhaust gas from the engine is removed through the exhaust gasaftertreatment device 18 and exhaust muffler 20. During the operation ofthis engine, the low-sulfur consumable lubricating oil compositioncirculates through the engine in the normal manner lubricating thedesired engine components. A portion of the low-sulfur consumablelubricating oil composition used in the engine collects in oil sump 22,and is pumped from oil sump 22 to fuel system 14, as indicated bydirectional arrow 28, where it is combined with the fuel. Theintroduction of the oil into the fuel may occur in one or more of thefuel tank, fuel return line, fuel injectors, intake manifold, positivecrankcase ventilation (PCV) system, exhaust gas recirculation (EGR)system, intake and/or exhaust valve guides, or air intake system of theengine 10.

The resulting combination of fuel and oil is comprised of about 0.01% toabout 5% by weight of said oil, and in one embodiment about 0.05% toabout 3% by weight, and in one embodiment about 0.1% to about 1.5% byweight, and in one embodiment about 0.1% to about 1% by weight, and inone embodiment about 0.1% to about 0.7% by weight, and in one embodimentabout 0.1% to about 0.5% by weight, and in one embodiment about 0.2% toabout 0.3% by weight of said oil, with the remainder being fuel.

Alternatively (as shown in the dashed line 30 in FIG. 1), the portion ofthe low-sulfur consumable lubricating oil composition removed from theoil sump 22 may be advanced to the exhaust gas system where it iscombined with the exhaust gas at any point in the exhaust gas systemupstream of (i.e., prior to entry into) the exhaust gas aftertreatmentdevice 18.

The sequence of removing used oil from the engine and replacing it withnew oil may be performed continuously or intermittently during theoperation of the engine.

The fuel may be a normally liquid or gaseous fuel. These includehydrocarbonaceous petroleum distillate fuels such as motor gasoline asdefined by ASTM Specification D439 and diesel fuel as defined by ASTMSpecification D396. Normally liquid hydrocarbon fuels containingmaterials such as alcohols, ethers, organo-nitro compounds and the like(e.g., methanol, ethanol, diethyl ether, methyl ethyl ether,nitromethane) are also within the scope of this invention as are liquidfuels derived from vegetable or mineral sources such as corn, alfalfa,shale and coal. Examples of such mixtures include gasoline and ethanol,and diesel fuel and ether.

In one embodiment, the fuel is gasoline, that is, a mixture ofhydrocarbons having an ASTM distillation range from about 60° C. at the10% distillation point to about 205° C. at the 90% distillation point.In one embodiment, the gasoline fuel composition is an unleaded fuelcomposition. In one embodiment, the gasoline is a chlorine-free orlow-chlorine gasoline characterized by a chlorine content of no morethan about 10 ppm. In one embodiment, the gasoline is a low-sulfur fuelcharacterized by a sulfur content of no more than about 300 ppm, and inone embodiment no more than about 150 ppm, and in one embodiment no morethan about 100 ppm, and in one embodiment no more than about 50 ppm, andin one embodiment no more than about 25 ppm, and in one embodiment nomore than about 10 ppm.

The diesel fuel that is useful may be any diesel fuel. These dieselfuels typically have a 90% point distillation temperature in the rangeof about 300° C. to about 390° C., and in one embodiment about 330° C.to about 350° C. The viscosity for these fuels typically ranges fromabout 1.3 to about 24 centistokes at 40° C. The diesel fuels can beclassified as any of Grade Nos. 1-D, 2-D or 4-D as specified in ASTMD975. These diesel fuels may contain alcohols and esters. In oneembodiment the diesel fuel has a sulfur content of up to about 0.05% byweight (low-sulfur diesel fuel) as determined by the test methodspecified in ASTM D2622-87.

The fuel compositions may contain one or more fuel additives known inthe art for enhancing the performance of the fuel. These include depositpreventers or modifiers, dyes, cetane improvers, antioxidants such as2,6-di-tertiary-butyl-4-methyl-phenol, corrosion inhibitors such asalkylated succinic acids and anhydrides, bacteriostatic agents, guminhibitors, metal deactivators, demulsifiers, upper cylinder lubricants,anti-icing agents, ashless dispersants, and the like.

The fuel additives may be added directly to the fuel, or they may bediluted with a normally liquid organic diluent such as naphtha, benzene,toluene, or xylene to form an additive concentrate prior to addition tothe fuel. These concentrates typically contain from about 10% to about90% by weight diluent.

The fuel may be a gaseous fuel such as natural gas. The fuel may bestored as a liquid and used in its gaseous form. Examples includepropane and dimethyl ether.

EXAMPLE 1

Engine tests are conducted using a 2.3 liter, overhead cam,four-cylinder Ford electronic fuel injected engine. The engine isoperated at low- and mid-range speeds and temperatures for 288 hours,simulating stop-and-go urban and moderate freeway driving. The testconditions involve 72 cycles, each being 4 hours in length and having 3stages, for a total test time of 288 hours. The length of time andoperating conditions for each stage is as follows:

Speed Load Coolant Stage Hours (ppm) (kW) Oil (° C.) (° C.) 1 2.00 250025.0 68.3 51.7 2 1.25 2500 25.0 98.9 85.0 3 0.75  750 0.7 46.1 46.1

The valve train (i.e, cam shaft, valve lifters, rocker arms, valvestems, etc.) is separated from the crankcase (i.e., crankshaft, pistons,connecting rods, etc.) to simulate a split engine design. The standardCu—Pb bearings are replaced with Al—Sn bearings. A Johnson MattheyJM220K catalyst is installed in the exhaust system.

The fuel is an unleaded gasoline fuel composition having a sulfurcontent of 28 ppm. The valve train is lubricated using a conventionallubricating oil composition. The crankcase is lubricated using thefollowing ashless lubricating oil compositions (in the table below allnumerical values provided for the components of the composition (exceptthe foam inhibitor) are in percent by weight).

A B Base oil - - SAE 5W-30 Polyalpha olefin oil mixture 83.4 83.4 (80%by wt. polyalphaolefln having viscosity of 6 cSt @ 100° C. and 20% bywt. polyalphaolefin having viscosity of 4 cSt 100° C.) Dispersant - -Succinimide derived from high 14.3 — vinylidene polyisobutene (numberaverage molecular weight (Mn) equal to about 1000) substituted succinicanhydride and tetraethylene pentamine (Nitrogen content = 3.3% by wt.)dispersed in oil (40% by wt. sulfur-free 100N (neutral) mineral oil)Dispersant - - Succinimide derived from high — 14.3 vinylidenepolyisobutene (Mn equal to about 1000) substituted succinic anhydrideand tetraethylene pentamine (Nitrogen content = 3.3% by wt.) dispersedin oil (40% by wt. 100N mineral oil) Viscosity modifier -- LZ 7067 (aproduct of Lubrizol 0.8 0.8 identified as an olefin copolymer) Diluentoil (sulfur-free 100N mineral oil) 0.38 — Diluent oil (100N mineral oil)— 0.38 Corrosion inhibitor -- Pluradyne FL11 (product of 0.02 0.02 BASFidentified as an ethylene oxide-propylene oxide copolymer) Antioxidant-- Nonylated diphenylamine 0.6 0.6 Antioxidant -- 4,4′-methylene bis2,6-di-t-butyl phenol 0.5 0.5 Foam inhibitor -- Polydimethyl siloxanedispersed in 50 ppm 50 ppm kerosene (90% kerosene) Physical properties:Viscosity @ 100° C., cSt 11.43 11.59 Viscosity @ 40° C., cSt 68.20 70.71Viscosity index 162 159 High Temperature/High Sheer @ 150° C., cP 3.503.46 (ASTM D 4683) Chemical properties: % P, Zn, Si, Ca, Mg, Na, Halogennil nil % N, wt % 0.492 0.492 Si, ppm 2 2 S, ppm 11 272

The crankcase of the engine is lubricated using lubricating oilcomposition A. A first peristaltic pump continuously removes usedlubricating oil composition A from the crankcase of the engine at a rateof 0.55 liter per 24 hours (0.0229 liter per hour) and advances the usedoil to the fuel tank where it is mixed with the gasoline in the fueltank. A second peristaltic pump continuously adds fresh lubricating oilcomposition A to the crankcase of the engine at a rate of 0.55 liter per24 hours to replace the used oil that is removed. The fuel usage per 24hour interval is 110 liters, the oil usage per 24 hour interval being0.55 liter. The content of the oil in the fuel is 0.5% by weight. TheNO_(x) level in the exhaust gas is measured before entering the catalystand after passing through the catalyst with the results being plotted inFIG. 2.

In a comparative test run, the crankcase of the engine is lubricatedusing the lubricating composition B. The gasoline fuel compositioncontains 0.5% by weight of a freshly blended sample of lubricating oilcomposition B. The fuel usage per 24 hour interval is 110 liters, theoil usage per 24 hour interval being 0.55 liter. At 24 hour intervals,0.71 liter samples of crankcase oil are removed, and replaced with 0.55liter of new oil plus 0.16 liter of the removed oil. The NO_(x) level inthe exhaust gas is measured before entering the catalyst and afterpassing through the catalyst with the results being plotted in FIG. 3.This test is provided for purposes of comparison.

The foregoing illustrates an advantage of the inventive method which isto provide a low level of NO_(x) in the exhaust gas of an internalcombustion engine equipped with an exhaust gas aftertreatment device.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A low-sulfur consumable lubricating oilcomposition, comprising: a poly-alpha-olefin base oil; from about 1% toabout 25% by weight of an acylated nitrogen-containing compound having asubstituent of at least about 10 aliphatic carbon atoms; and a sulfurcontent of about 5 to about 250 ppm; said composition beingcharacterized by the absence of an extreme-pressure additive comprisedof metal and phosphorus.
 2. The composition of claim 1 wherein saidlubricating oil composition is comprised of components that add only C,H, O or N, and optionally Si to said composition.
 3. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas a viscosity of up to about 16.3 cSt at 100° C.
 4. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W,5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40 or10W-50.
 5. The composition of claim 1 wherein said low-sulfur consumablelubricating oil composition has a high-temperature/high-shear viscosityat 150° C. of up to about 4 centipoise.
 6. The composition of claim 1wherein said acylated nitrogen-containing compound is derived from acarboxylic acylating agent and at least one amino compound containing atleast one —NH— group, said acylating agent being linked to said aminocompound through an imido, amido, amidine or salt linkage.
 7. Thecomposition of claim 6 wherein said amino compound is analkylenepolyamine represented by the formula:

wherein U is an alkylene group of from about 2 to about 10 carbon atoms;each R is independently a hydrogen atom, a hydrocarbyl group, ahydroxy-substituted hydrocarbyl group, or an amine-substitutedhydrocarbyl group containing up to about 30 carbon atoms, with theproviso that at least one R is a hydrogen atom; and n is 1 to about 10.8. The composition of claim 6 wherein said carboxylic acylating agent isa mono- or polycarboxylic acid or anhydride containing an aliphatichydrocarbyl substituent of at least about 30 carbon atoms.
 9. Thecomposition of claim 1 wherein said acylated nitrogen-containingcompound is a polyisobutene substituted succinimide containing at leastabout 50 aliphatic carbon atoms in the polyisobutene group.
 10. Thecomposition of claim 1 wherein said acylated-nitrogen containingcompound has a chlorine content of no more than about 50 ppm.
 11. Thecomposition of claim 1 wherein said low-sulfur consumable lubricatingoil composition is a low-ash lubricating oil composition which furthercomprises an ash-producing detergent or dispersant.
 12. The compositionof claim 1 wherein said low-sulfur consumable lubricating oilcomposition is characterized by the absence of an ash-producingdetergent or dispersant.
 13. The composition of claim 1 wherein saidlow-sulfur consumable lubricating oil composition is comprised of atleast one ashless detergent or dispersant, corrosion-inhibiting agent,antioxidant, viscosity modifier, pour point depressant, frictionmodifier, fluidity modifier, or anti-foam agent.
 14. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas a sulfur content of about 5 to about 50 ppm.
 15. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas a chlorine content of no more than about 10 ppm.
 16. A method ofoperating an internal combustion engine equipped with an exhaust gasaftertreatment device, said method comprising: (A) operating said engineusing a normally liquid or gaseous fuel; (B) lubricating said engineusing a low-sulfur consumable lubricating oil composition, said oilcomposition comprising: a base oil; an acylated nitrogen-containingcompound having a substituent of at least about 10 aliphatic carbonatoms; and a sulfur content of about 5 to about 250 ppm; said oilcomposition being characterized by the absence of an extreme-pressureadditive comprised of metal and phosphorus; (C) removing part of saidlow-sulfur consumable lubricating oil composition from said engine, saidremoved part of said low-sulfur consumable lubricating oil composition(i) being combined with said fuel and consumed with said fuel as saidengine is operated or (ii) being combined with the exhaust gas from saidengine and removed from said engine with said exhaust gas; and (D)adding an additional amount of said low-sulfur consumable lubricatingoil composition to said engine to replace said removed part of saidlow-sulfur consumable lubricating oil composition.
 17. The method ofclaim 16 wherein the combination of said fuel composition and saidlow-sulfur consumable lubricating oil composition formed in step (C) iscomprised of about 0.01% to about 5% by weight of said low-sulfurconsumable lubricating oil composition.
 18. The method of claim 16wherein during step (C) said removed part of said low-sulfur consumablelubricating oil composition is introduced into said fuel composition inthe fuel tank, fuel return line, fuel injectors, intake manifold,positive crankcase ventilation system, exhaust gas recirculation system,or air intake system of the engine.
 19. The method of claim 16 whereinsaid engine is a compression ignition engine.
 20. The method of claim 16wherein said fuel is a diesel fuel composition.
 21. The method of claim16 wherein said fuel composition is a low-sulfur diesel fuelcomposition.
 22. The method of claim 16 wherein said engine is a sparkignition engine.
 23. The method of claim 16 wherein said fuel is agasoline fuel composition.
 24. The method of claim 16 wherein said fuelis an unleaded gasoline fuel composition.
 25. The method of claim 16wherein said fuel is a gasoline fuel composition having a sulfur contentof up to about 300 ppm.
 26. The method of claim 16 wherein said fuel isa gasoline fuel composition having a chlorine content of no more thanabout 10 ppm.
 27. A method of operating an internal combustion engineequipped with an exhaust gas aftertreatment device, said methodcomprising: (A) operating said engine using a normally liquid or gaseousfuel; (B) lubricating said engine using a low-sulfur consumablelubricating oil composition, said oil composition comprising: a baseoil; an acylated nitrogen-containing compound having a substituent of atleast about 10 aliphatic carbon atoms; and a sulfur content of about 5to about 250 ppm; said oil composition being characterized by theabsence of an extreme-pressure additive comprised of metal andphosphorus; (C) removing part of said low-sulfur consumable lubricatingoil composition from said engine, said removed part of said low-sulfurconsumable lubricating oil composition being combined with the exhaustgas from said engine upstream of said exhaust gas aftertreatment deviceand removed from said engine with said exhaust gas; and D) adding anadditional amount of said low-sulfur consumable lubricating oilcomposition to said engine to replace said removed part of saidlow-sulfur consumable lubricating oil composition.